Re: [PATCH] mtd: nand: reduce the warning noise when the ECC is too weak

[Josh Wu <josh.wu@atmel.com>]

Hi, Brian

On 7/14/2014 1:22 PM, Brian Norris wrote:
> On Wed, Jul 02, 2014 at 03:16:32PM +0200, Thomas Petazzoni wrote:
>> In commit 67a9ad9b8a6f ("mtd: nand: Warn the user if the selected ECC
>> strength is too weak"), a check was added to inform the user when the
>> ECC used for a NAND device is weaker than the recommended ECC
>> advertised by the NAND chip. However, the warning uses WARN_ON(),
>> which has two undesirable side-effects:
>>
>>   - It just prints to the kernel log the fact that there is a warning
>>     in this file, at this line, but it doesn't explain anything about
>>     the warning itself.
>>
>>   - It dumps a stack trace which is very noisy, for something that the
>>     user is most likely not able to fix. If a certain ECC used by the
>>     kernel is weaker than the advertised one, it's most likely to make
>>     sure the kernel uses an ECC that is compatible with the one used by
>>     the bootloader, and changing the bootloader may not necessarily be
>>     easy. Therefore, normal users would not be able to do anything to
>>     fix this very noisy warning, and will have to suffer from it at
>>     every kernel boot. At least every time I see this stack trace in my
>>     kernel boot log, I wonder what new thing is broken, just to realize
>>     that it's once again this NAND ECC warning.
>>
>> Therefore, this commit turns:
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 1 at /home/thomas/projets/linux-2.6/drivers/mtd/nand/nand_base.c:4051 nand_scan_tail+0x538/0x780()
>> Modules linked in:
>> CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0-rc3-dirty #4
>> [<c000e3dc>] (unwind_backtrace) from [<c000bee4>] (show_stack+0x10/0x14)
>> [<c000bee4>] (show_stack) from [<c0018180>] (warn_slowpath_common+0x6c/0x8c)
>> [<c0018180>] (warn_slowpath_common) from [<c001823c>] (warn_slowpath_null+0x1c/0x24)
>> [<c001823c>] (warn_slowpath_null) from [<c02c50cc>] (nand_scan_tail+0x538/0x780)
>> [<c02c50cc>] (nand_scan_tail) from [<c0639f78>] (orion_nand_probe+0x224/0x2e4)
>> [<c0639f78>] (orion_nand_probe) from [<c026da00>] (platform_drv_probe+0x18/0x4c)
>> [<c026da00>] (platform_drv_probe) from [<c026c1f4>] (really_probe+0x80/0x218)
>> [<c026c1f4>] (really_probe) from [<c026c47c>] (__driver_attach+0x98/0x9c)
>> [<c026c47c>] (__driver_attach) from [<c026a8f0>] (bus_for_each_dev+0x64/0x94)
>> [<c026a8f0>] (bus_for_each_dev) from [<c026bae4>] (bus_add_driver+0x144/0x1ec)
>> [<c026bae4>] (bus_add_driver) from [<c026cb00>] (driver_register+0x78/0xf8)
>> [<c026cb00>] (driver_register) from [<c026da5c>] (platform_driver_probe+0x20/0xb8)
>> [<c026da5c>] (platform_driver_probe) from [<c00088b8>] (do_one_initcall+0x80/0x1d8)
>> [<c00088b8>] (do_one_initcall) from [<c0620c9c>] (kernel_init_freeable+0xf4/0x1b4)
>> [<c0620c9c>] (kernel_init_freeable) from [<c049a098>] (kernel_init+0x8/0xec)
>> [<c049a098>] (kernel_init) from [<c00095f0>] (ret_from_fork+0x14/0x24)
>> ---[ end trace 62f87d875aceccb4 ]---
>>
>> Into the much shorter, and much more useful:
>>
>> nand: WARNING: MT29F2G08ABAEAWP: the ECC used on your system is too weak compared to the one required by the NAND chip
>>
>> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Pushed to linux-mtd.git, for 3.16 I think. Thanks!

Excuse me that to ask a question which is not related with the code.

I find this fix is not in l2-mtd.git but only in linux-mtd.git. So I 
wondering how the patch is merged in linux mainline and stable tree.

Will the linux-mtd.git be merged in linux mainline and stable git tree 
before v3.16 release? So the l2-mtd.git can rebase on the merged tag.

Am I understand the flow correctly?

Thanks in advance.

Best Regards,
Josh Wu
>
> Brian
>
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